The complete DNA sequence of the Dictyostelium discoideum genome will be determined over a five-year period at an average cost of 21 cents per base. The thirty-four million basepair sequence will be highly accurate (greater than 99.99 percent) and contain few gaps. The sequence data will be analyzed for gene-content, richly annotated, and immediately released to the public. These data will facilitate subsequent molecular analyses of gene function in this organism and will be indispensable for defining genes present in all eukaryotic organisms, including humans. A combined clone-mapping and shotgun-sequencing strategy will be employed to obtain complete sequences of Bacterial Artificial Chromosomes (BACs) carrying large segments (4 percent) of the genome. The shotgun strategy used will minimize redundant sequencing, and thus increase efficiency and lower costs. Gaps in the sequence will be filled by sequencing additional BAC clones and by sequencing selected clones from an independent library of Yeast Artificial Chromosomes (YACs), which have already been ordered along the Dictyostelium chromosomes and represent the genome with high fidelity. There are compelling reasons to sequencing the complete genome of Dictyostelium. Studies in over 150 laboratories world-wide have shown that these soil amoebae are an excellent system for the analysis of the molecular mechanisms of cell motility, signal transduction, cell-type differentiation and a host of developmental processes. As the total complement of genes is uncovered, tests of their function can proceed logically in the context of a rich knowledge-base in these areas. Detailed molecular descriptions of the functions of genes described in other species as well as "pathfinder" genes can be worked out in the relatively simple setting of Dictyostelium cell physiology. As the functions for these genes are defined in Dictyostelium additional clues to their function in other species will be revealed. This will inevitably improve our ability to interpret the potential function of human genes, their roles in normal physiology and development, and may shed light the problems created by aberrant gene products in the pathogenesis of various diseases.